The present invention relates to certain fatty acid esters and their preparation, and to the use of such compounds or pharmaceutical formulations thereof in medicine in a mammal, including man, as, for example, anti-inflammatory or immunomodulatory agents.
Fatty acids are generally known to include the carboxylic acids that make up glycerides, such as triacylglycerols, the carboxylic esters comprised in the fat storage cells of plants and animals. Many such fatty acids are straight-chain compounds, having from three to eighteen carbon atoms (C3-C18); except for the C3 and C5 compounds, only acids containing an even number of carbon atoms are present in substantial amounts, due to their biosynthesis. There are both saturated and unsaturated fatty acids, such as the unsaturated C18 oleic, xcex1-linoleic and xcex3-linolenic (GLA) fatty acids, each having one, two and three carbon-carbon double bonds, respectively. Conventional notation therefore refers to these acids as 18:1, 18:2 and 18:3 fatty acids, respectively. The configuration about these double bonds is usually cis, which lowers the melting point of the corresponding fat (compared to the corresponding saturated and trans compounds).
Besides these short- and medium-chain fatty acids, those with longer chains, such as C16-C24, are also known and have been investigated, particularly those available from fish oils, such as eicosapentaenoic (EPA, 20:5 (nxe2x88x923)) and docosahexaenoic (DHA, 22:6 (nxe2x88x923)) acids, where, in (nxe2x88x92x), x indicates the position of the first carbon-carbon double bond with respect to the terminal methyl group on the fatty acid.
As well as their dietary metabolism and their potential dietary use, some fatty acids have been investigated in relation to medical conditions such as schizophrenia (GLA and DHA) and bipolar disorder (EPA and DHA). Some have also been proposed for improving the transport of biologically active drugs (xe2x80x98bioactivesxe2x80x99) across lipid membranes by linking the bioactive either directly or indirectly to certain fatty acids. For example, in PCT patent specification no. WO 96/34846, it is disclosed that any of the essential fatty acids (which include GLA, DHA and EPA) or any other C12-30 fatty acid having at least two carbon-carbon double bonds may be so used. Amongst a wide range of possible bioactives and (12-30:xe2x89xa72) fatty acids mentioned in that specification is specifically disclosed GLA-GLA, being a pair of GLA molecules linked via a propane-1,3-diol moiety, namely 1,3-(di-z,z,z,-octadeca-6,9,12-trienoyloxy)propane. However, no biological results in any pharmacological tests are shown for GLA-GLA, other than a report that it was administered to rats and mice up to 10 g/kg without evidence of diarrhea (ie absence of toxicity, rather than presence of therapeutic effect).
Nevertheless, GLA-GLA is mentioned as one possible propane-1,3-diol compound having a broad range of listed uses, including the treatment of inflammatory diseases. However, as reported hereinbelow with particular reference to Example 4, we found that GLA:GLA had no effect in our tests for anti-inflammatory activity. Accordingly, it might be expected that other combinations of (12-30:xe2x89xa72) fatty acids linked via a propane-1,3-diol moiety might also not show anti-inflammatory action, especially where such action was not already demonstrated for at least one of the fatty acid moieties involved.
Furthermore, no possibility of using other types of fatty acids, such as those having only one carbon-carbon double bond, is contemplated in WO 96/34846. One such different type of fatty acid is nervonic acid. Nervonic acid (24:1 (nxe2x88x929)) is cis (or z)-tetracos-15-enoic acid; it is not classed as an essential fatty acid and has only one unsaturated Cxe2x95x90C bond. It plays a part in the biosynthesis of myelin and is one of the major fatty acids in brain sphingolipids. Nervonic acid has therefore been implicated in diseases involving demyelination, such as adrenoleukodystrophy (ALD) and multiple sclerosis (MS). It has therefore been proposed to administer nervonic acid or a source thereof as a pharmaceutical formulation thereof to patients suffering from demyelinating conditions (as described in PCT published specification no. WO 91/07955), or to provide nervonic acid or a functional derivative thereof as a dietary supplement, for example, as baby or infant feeds, or to pregnant or lactating women (as described in PCT published specification no PCT/GB95/01985). Although the precise causes of MS are not yet known, strong evidence now suggests that MS results from an autoimmune process triggered by an environmental factor, possibly a non-specific viral infection, in a genetically susceptible individual, in which immune cells mistake myelin as a foreign invader and attack it. This process produces perivascular inflammation in the CNS and eventually damages not only myelin but also underlying nerve tissue. However, nervonic acid is not known to have any general effect on inflammation or inflammatory diseases.
As a result of damage to the myelin and nerve tissue, the blood-brain barrier is disrupted, enabling activated T-cells to enter the brain and recruit other lymphocytes. Activated T-cells release lymphotoxin, interferon gamma (IFN-xcex3) and other inflammatory cytokines. Lymphotoxin can damage oligodendrocytes, and IFN-xcex3, which has been shown to provoke MS exacerbations, stimulates the immune system in a number of ways thought to aggravate MS. Oligodendrocyte cells synthesise myelin-specific proteins and lipids, and their role is critical for both normal myelin sheath formation and normal brain function.
For example, IFN-xcex3 augments expression of major histocompatibility complex (MHC) class II molecules on macrophages, and induces their expression on astrocytes, microglia and endothelial cells. Antigenic myelin peptides associated with these MHC molecules are recognised by T-cells, which proliferate in response to antigen presentation, amplifying the immune response.
Macrophages activated by IFN-xcex3 also release tumour necrosis factor (TNF), which has been shown to damage oligodendrocytes in vitro. In addition, cytokines, proteinases and lipases are secreted, and B-cells are induced to synthesise antibodies. This response results in demyelination and gliosis, which causes nerve impulses to be slowed or halted and produces the symptoms of MS.
It has now surprisingly been found that certain derivatives of nervonic acid possess anti-inflammatory and/or immunomodulatory activity. Furthermore, some of these derivatives assist in the passage of nervonic acid across the blood-brain barrier.
Accordingly, the present invention provides a compound of formula (I): 
wherein R is hydrogen (H) or a residue of a carboxylic acid or a salt of the compounds where R is H.
The definition of formula (I) also includes, where applicable, individual isomers and mixtures thereof; and derivatives (especially bioprecursors or pro-drugs) thereof.
The term xe2x80x9cbioprecursorxe2x80x9d or xe2x80x9cpro-drugxe2x80x9d means a pharmacologically acceptable derivativexe2x80x94eg an ester (such as a biolabile ester derivative of a xe2x80x94COOH group)xe2x80x94that is converted in vivo to a compound of the present invention. Suitable pro-drugs can be determined by reference to Goodman and Gilman, The Pharmacological Basis of Therapeutics, 8th Edition, McGraw-Hill, Int. Ed. 1992, particularly xe2x80x9cBiotransformation of Drugsxe2x80x9d, pp. 13-15.
The carboxylic acid referred to in the definition of R preferably has from 1 to 26 carbon atoms, and may be straight- or branched-chain, saturated or unsaturated. More preferably, the carboxylic acid is straight chain and is selected from the group consisting of mono- and poly-unsaturated fatty acids. Particularly preferred are compounds of formula (I) wherein R is a residue of a C18 to C24 mono- or poly-unsaturated fatty acid, having from 1 to 6 carbon-carbon double bonds. Especially preferred is when R is a residue of nervonic acid (24:1(nxe2x88x929)), docosahexaenoic acid (22:6(nxe2x88x923)) or xcex3-linolenic acid (18:3(nxe2x88x926)), where x in (nxe2x88x92x) indicates the position of the first double bond with respect to the terminal methyl group of the fatty acid.
It will be understood by the person skilled in the art that the compounds of formula (I) wherein R is H are useful as intermediates in the synthesis of other compounds of formula (I). Accordingly, the present invention provides a method for the preparation of the compounds of formula (I) wherein R is a residue of a carboxylic acid, which method comprises reacting the compound of formula (IA), namely, 1-(z-15-tetracosenoyloxy)-3-hydroxypropane: 
with the corresponding carboxylic acid of formula Rxe2x80x94H, wherein R is as defined for formula (I).
Suitable conditions for this esterification reaction are known to those skilled in the art and include the presence of hypophosphorous acid, preferably with heating to reflux under an inert atmosphere, such as nitrogen.
The compound of formula (IA) may itself be prepared in conventional manner, such as from the reaction of the acid chloride of nervonic acid (ie CH3xe2x80x94(CH2)7xe2x80x94CHxe2x95x90CHxe2x80x94(CH2)13xe2x80x94COCl) with propane-1,3-diol in the presence of a base, such as an organic base, for example, trialkylamines eg triethylamine and tributylamine, and pyridine, 2,6-dimethylpyridine and quinoline, preferably in an organic aprotic solvent, such as a halogenated alkane, for example, dichloromethane, ether, tetrahydrofuran and toluene. The reaction is preferably carried out with cooling, such as to about 0xc2x0 C., under an inert atmosphere, such as nitrogen.
The acid chloride of nervonic acid (z-15-tetracosenoyl chloride) can be prepared in conventional manner from nervonic acid and thionylchloride, phosphorous trichloride or, especially, phosphorous pentachloride, preferably in a polar solvent such as an ether in anhydrous conditions and preferably under an inert atmosphere.
In the case of the preparation of the compound of formula (I) wherein R is the residue of nervonic acid, the two-step process described above can be carried out in a single pot from nervonic acid, propane-1,3-diol and, for example, hypophosphorous acid.
Nervonic acid is commercially-available from Aldrich Chemicals, UK or is otherwise available as described, for example, in U.S. patent specification no. U.S. Pat. No. 5,194,448 or published PCT patent specification no. PCT/GB95/01985.
The compounds of formula (I) wherein R is other than H, namely, compounds of formula (IB): 
wherein R1 is a residue of a carboxylic acid have, as mentioned before, surprisingly been found to possess anti-inflammatory and/or immunomodulatory activity.
Preferred carboxylic acid residues are as described hereinabove with respect to the definition of R.
Accordingly, the present invention provides the following specific compounds of formula (IB):
1-(z-15-tetracosenoyloxy)-3-(z,z,z-6,9,12-octadecatrienoyloxy)propane (hereinafter referred to as NA:GLA);
1-(z-15-tetracosenoyloxy)-3-(z-4,7,10,13,16,19-docosahexaenoyloxy)propane (hereinafter referred to as NA:DHA); and
1,3-di-(z-15-tetracosenoyloxy)propane (hereinafter referred to as NA:NA).
By xe2x80x98anti-inflammatoryxe2x80x99 herein is meant the ability to reduce, ameliorate or prevent inflammation or an inflammatory response. By xe2x80x98immunomodulatoryxe2x80x99 herein is meant the ability to modulate an immune response, such as by suppressing or stimulating such a response. It will be understood by those skilled in the art that both anti-inflammatory and immunomodulatory activity may be desirable for the treatment or prevention of some medical conditions.
The anti-inflammatory and/or immunomodulatory effects of the compounds of formula (IB) can be observed in the experimental allergic encephaolmyelitis (EAE) tests described in more detail hereinbelow in the Examples. EAE is an autoimmune inflammatory disease of the CNS characterised by perivascular and subpial inflammatory infiltrates and lesions of demyelination. It can be induced by immunisation with whole homogenised spinal cord or brain material, purified myelin or oligodendrocytes, purified components of myelin, combined with adjuvants. The use of adjuvants, such as Freund""s adjuvant, is necessary to enhance the immunological response that ultimately results in disease. Due to the relative ease of purification, myelin basic protein (MBP) and proteolipid protein (PLP), and their fragments, have been studied extensively as encephalitogens in EAE.
EAE models may be broadly classified as acute monophasic EAE or chronic relapsing EAE:
In acute EAE, susceptible animals injected with small doses of myelin antigens in complete Freund""s adjuvant (CFA) succumb to paralytic disease within 10 to 14 days. The onset of disease is observed as loss of tone of the tail and/or mild paralysis of the hind feet, progressing to muscle wasting in the haunches and lower back. In severe cases, paralysis may spread to the forelimbs. If the animals do not become moribund, the severity of paralysis decreases and the animals recover. Classic acute EAE can be observed in Lewis rats; such models are ideal to study the effects of drug and/or immunotherapy aimed at reducing acute CNS inflammation.
The clinical grading and classification of neurological deficit depends on the strain of animal used and the course of the disease. A 0 to 6 point grading is generally used, ranging from asymptomatic (0) to death (6).
Prior to onset of clinical signs, animals lose weight, and examination of the CNS reveals mononuclear cell infiltration, particularly in the spinal cord. Following the onset of clinical signs, increasing numbers of mononuclear cells infiltrate the CNS and accumulate in the subpial areas of the spinal cord prior to infiltration of the parenchyma. Immunohistochemistry and cell isolation techniques have identified the predominant cells as macrophages and CD4+ T cells. It is noteworthy that demyelination is not a classic sign of acute EAE, and therefore this test is indicative of anti-inflammatory/immunomodulatory activity in general, rather than only of that which might accompany demyelinating diseases.
Chronic EAE is characterised by a continuation of neurological deficit without recovery, following an episode of acute EAE.
Alternatively, full recovery (remission) occurs after the acute phase, which is followed by phases of clinical and histological disease and further remissions. This is chronic relapsing (and remitting) EAE, which is more closely resembling of multiple sclerosis symptoms than the acute model. Although chronic relapsing EAE has been characterised in many species, mouse models have the advantage of a well-characterised immune system and the availability of a wide range of immunological reagents with which to probe the disease.
In addition to the inflammatory effects existing with EAE, chronic relapsing EAE (CREAE) presents primary demyelination in these inflammatory areas, particularly pronounced in a relapse phase.
The very positive results obtained in the acute EAE tests with NA:NA demonstrate that the use of the propane-1,3-diol moiety as a linker between the two fatty acyl moieties is of major importance, since glyceryl trinervonate (GTN), which consists of three fatty acyl moieties bound to a glycerol backbone, did not show any effect on the course of acute EAE. However, it is not enough to assume that the mere presence of the propane-1,3-diol moiety is itself sufficient to give rise to positive results. We have found that NA:GLA also gave rise to positive results, whereas tests using GLA:GLA showed absence of effect. This is surprising, since the disclosure of PCT patent specification no. WO 96/34846, discussed above, might lead to the expectation that GLA:GLA would give particularly beneficial biological results. Simply linking together two fatty acid moieties (R1) via a propane-1,3-diol moiety therefore does not necessarily result in a compound having immunomodulatory and/or anti-inflammatory activity.
Therefore, propane-1,3-diol derivatives of nervonic acid would seem to have unpredictable and differing activities compared to those of fatty acids having two or more unsaturated Cxe2x95x90C bonds. A structure-activity relationship for NA:NA has been established and it has also been shown that nervonic acid, in the form of the derivatives NA:NA and NA:GLA, shows general anti-inflammatory activity, which has not been shown before.
Accordingly, the compounds of formula (IB) may be used in the relief of rheumatoid arthritis, rheumatoid spondylitis, osteroarthritis, gouty arthritis and other arthritic conditions; inflamed joints; eczema and other inflammatory skin conditions; inflammatory eye conditions including conjunctivitis; pyresis and other conditions associated with inflammation, including the reduction of tissue necrosis in chronic inflammation, the suppression of tissue rejection following transplant surgery, Crohn""s disease and ulcerative colitis.
The compounds of formula (IB) may also be used in the treatment or prophylaxis of airway inflammatory conditions such as asthma and bronchitis. Other conditions, which are suitable for treatment by an immunomodulator, include systemic lupus erythematosis; multiple sclerosis; myasthenia gravis; progressive systemic sclerosis; atopic dermatitis; hyperimmunoglobin E; hepatitis B antigen negative chronic active hepatitis; Hashimoto""s thyroiditis; familial Mediterranean fever; Grave""s disease; autoimmune haemolytic anaemia; primary biliary cirrhosis; and inflammatory bowel disease. Further conditions, suitable for treatment by an immunostimulant, include any wherein the immune system is compromised, disabled or dysfunctional, such as in AIDS patients, and those associated with viral infections, such as HIV.
Preferred compounds of formula (IB) for use as an anti-inflammatory and/or immunosuppressant include NA:NA and NA:GLA, especially, NA:GLA; preferred for immunostimulant use is NA:DHA.
The amount required of a compound of formula (IB) (the active ingredient) for therapeutic effect will, of course, vary both with the particular compound, the route of administration and the mammal under treatment. A suitable dose of a compound of formula (IB) for a mammal suffering from a condition as defined hereinbefore is in the range of from 0.1 to 1000 mg of base per kilogram body weight, the most preferred dosage being 0.5 to 500 mg/kg of mammal body weight, such as from 1 to 50 mg/kg, for example 5 to 25 mg/kg; administered two or three times daily.
In the case of the treatment or prophylaxis of inflammatory airway conditions, a suitable anti-asthmatic dose of a compound of formula (IB) is 1 mg to 10 mg of base per kilogram body weight, the most preferred dosage being 1 mg to 5 mg/kg of mammal body weight, for example from 1 to 2 mg/kg.
While it is possible for an active ingredient to be administered alone as the raw chemical, it is preferable to present it as a pharmaceutical formulation. The formulations, both for veterinary and for human medical use, of the present invention comprise an active ingredient in association with a pharmaceutically acceptable carrier therefor and optionally other therapeutic ingredient(s). The carrier(s) must be xe2x80x98acceptablexe2x80x99 in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.
Conveniently, the active ingredient comprises from 0.1% to 99.9% by weight of the formulation. Suitably, unit doses of a formulation contain between 0.1 mg and 1 g of the active ingredient. Preferably, the formulation is suitable for administration from one to six, such as two to four, times per day. For topical administration, the active ingredient preferably comprises from 1% to 2% by weight of the formulation but the active ingredient may comprise as much as 10% w/w. Formulations suitable for nasal or buccal administration, such as the self-propelling powder-dispensing formulations described hereinafter, may comprise 0.1 to 20% w/w, for example about 2% w/w of active ingredient.
The formulations include those in a form suitable for oral, ophthalmic, rectal, parenteral (including subcutaneous, vaginal, intraperitoneal, intramuscular and intravenous), intra-articular, topical, nasal or buccal administration.
The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing the active ingredient into association with the carrier, which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing the active ingredient into association with a liquid carrier or a finely divided solid carrier or both, and then, if necessary, shaping the product into the desired formulation.
Formulations of the present invention suitable for oral administration may be in the form of discrete units such as capsules, cachets, tablets or lozenges, each containing a predetermined amount of the active ingredient; in the form of a powder or granules; in the form of a solution or a suspension in an aqueous liquid or non-aqueous liquid; or in the form of an oil-in-water emulsion or a water-in-oil emulsion. The active ingredient may also be in the form of a bolus, electuary or paste. For such formulations, a range of dilutions of the active ingredient in the vehicle is suitable, such as from 1% to 99%, preferably 5% to 50% and more preferably 10% to 25% dilution. Depending upon the level of dilution, the formulation will be either a liquid at room temperature (in the region of about 20xc2x0 C.) or a low-melting solid. For example, compositions where NA:GLA is the active ingredient are miscible in all proportions at room temperature, whereas those comprising NA:NA are liquids at room temperature when the concentration is at or below about 25%.
A tablet may be made by compressing or moulding the active ingredient optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing, in a suitable machine, the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, surface active or dispersing agent. Moulded tablets may be made by moulding, in a suitable machine, a mixture of the powdered active ingredient and a suitable carrier moistened with an inert diluent.
Formulations for rectal administration may be in the form of a suppository incorporating the active ingredient and a carrier such as cocoa butter, or in the form of an enema.
Formulations suitable for parenteral administration comprise a solution, suspension or emulsion, as described above, conveniently a sterile aqueous preparation of the active ingredient that is preferably isotonic with the blood of the recipient.
Formulations suitable for intra-articular administration may be in the form of a sterile aqueous preparation of the active ingredient, which may be in a microcrystalline form, for example, in the form of an aqueous microcrystalline suspension or as a micellar dispersion or suspension. Liposomal formulations or biodegradable polymer systems may also be used to present the active ingredient particularly for both intra-articular and ophthalmic administration.
Formulations suitable for topical administration include liquid or semi-liquid preparations such as liniments, lotions or applications; oil-in-water or water-in-oil emulsions such as creams, ointments or pastes; or solutions or suspensions such as drops. For example, for ophthalmic administration, the active ingredient may be presented in the form of aqueous eye drops, as for example, a 0.1-1.0% solution.
Drops according to the present invention may comprise sterile aqueous or oily solutions and may be prepared by dissolving the active ingredient in a suitable aqueous solution containing a bactericide and/or fungicidal agent and/or any other suitable preservative. The resulting solution may then be clarified by filtration, transferred to a suitable container, and then sealed and sterilised by autoclaving or maintaining at 90-100xc2x0 C. for half an hour. The solution may be sterilised by filtration and transferred to the container by an aseptic technique. Preservatives, bactericidal and fungicidal agents suitable for inclusion in the drops are phenylmercuric salts (0.002%), benzalkonium chloride (0.01%) and chlorhexidine acetate (0.01%). Suitable solvents for the preparation of an oily solution include glycerol, diluted alcohol and propylene glycol.
Lotions according to the present invention include those suitable for application to the eye. An eye lotion may comprise a sterile aqueous solution optionally containing a bactericide or preservative prepared by methods similar to those for the preparation of drops. Lotions or liniments for application to the skin may also include an agent to hasten drying and to cool the skin, such as an alcohol, or a softener or moisturiser such as glycerol or an oil such as castor oil or arachis oil.
Creams, ointments or pastes according to the present invention are semi-solid formulations of the active ingredient for external application. They may be made by mixing the active ingredient in granule or powdered form, alone or in solution or suspension in an aqueous or non-aqueous solution in suitable machinery, with a greasy or non-greasy basis. The basis may comprise one or more of a hard, soft or liquid paraffin, glycerol, beeswax, a metallic soap; a mucilage; an oil such as a vegetable oil, eg almond, corn, arachis, castor or olive oil; wool fat or its derivatives; or a fatty acid ester of a fatty acid together with an alcohol such as propylene glycol or macrogols. The formulation may also comprise a suitable surface-active agent, such as an anionic, cationic or non-ionic surfactant such as a glycol or polyoxyethylene derivatives thereof. Suspending agents such as natural gums may be incorporated, optionally with other inorganic materials, such as silicaceous silicas, and other ingredients such as lanolin.
Formulations suitable for administration to the nose or buccal cavity include those suitable for inhalation or insufflation, and include powder, self-propelling and spray formulations such as aerosols and atomisers. The formulations, when dispersed, preferably have a particle size in the range of 10 to 200xcexc.
Such formulations may be in the form of a finely comminuted powder for pulmonary administration from a powder inhalation device or self-propelling powder-dispensing formulations, where the active ingredient, as a finely comminuted powder, may comprise up to 99.9% w/w of the formulation. In the case of self-propelling solution and spray formulations, the effect may be achieved either by choice of a valve having the desired spray characteristics (ie being capable of producing a spray having the desired particle size) or by incorporating the active ingredient as a suspended powder of controlled particle size. Thus the formulation, instead of passing into the lungs, is largely retained in the nasal cavity. These self-propelling formulations may be either powder-dispensing formulations or formulations dispensing the active ingredient as droplets of a solution or suspension.
Self-propelling powder-dispensing formulations preferably comprise dispersed particles of solid active ingredient, and a liquid propellant having a boiling point of below 18xc2x0 C. at atmospheric pressure. The liquid propellant may be any propellant known to be suitable for medicinal administration and may comprise one or more lower alkyl hydrocarbons or halogenated lower alkyl hydrocarbons or mixtures thereof; chlorinated and fluorinated lower alkyl hydrocarbons are especially preferred. Generally, the propellant constitutes 50 to 99.9% w/w of the formulation whilst the active ingredient constitutes 0.1 to 20% w/w, for example, about 2% w/w, of the formulation.
The pharmaceutically acceptable carrier in such self-propelling formulations may include other constituents in addition to the propellant, in particular a surfactant or a solid diluent or both. Surfactants are desirable since they prevent agglomeration of the particles of active ingredient and maintain the active ingredient in suspension. Especially valuable are liquid non-ionic surfactants and solid anionic surfactants or mixtures thereof. Suitable liquid non-ionic surfactants are those having a hydrophile-lipophile balance (HLB, see Journal of the Society of Cosmetic Chemists Vol. 1 pp. 311-326 (1949)) of below 10, in particular esters and partial esters of fatty acids with aliphatic polyhydric alcohols, for instance, sorbitan mono-oleate and sorbitan trioleate, available commercially as xe2x80x98Span 80xe2x80x99 (Trade Name) and xe2x80x98Span 85xe2x80x99 (Trade Name), respectively. The liquid non-ionic surfactant may constitute from 0.01 up to 20% w/w of the formulation, though preferably it constitutes below 1% w/w of the formulation. Suitable solid anionic surfactants include alkali metal, ammonium and amine salts of dialkyl sulphosuccinate (where the alkyl groups have 4 to 12 carbon atoms) and alkyl benzene sulphonic acid (where the alkyl group has 8 to 14 carbon atoms). The solid anionic surfactants may constitute from 0.01 up to 20% w/w of the formulation, though preferably below 1% w/w of the composition. Solid diluents may be advantageously incorporated in such self-propelling formulations where the density of the active ingredient differs substantially from the density of the propellant; also, they help to maintain the active ingredient in suspension. The solid diluent is in the form of a fine powder, preferably having a particle size of the same order as that of the particles of the active ingredient. Suitable solid diluents include sodium chloride, sodium sulphate and sugars.
Formulations of the present invention may also be in the form of a self-propelling formulation wherein the active ingredient is present in solution. Such self-propelling formulations may comprise the active ingredient, propellant and co-solvent, and advantageously an antioxidant stabiliser. The propellant is one or more of these already cited above. Co-solvents are chosen for their solubility in the propellant, their ability to dissolve the active ingredient, and for their having the lowest boiling point consistent with these above-mentioned properties. Suitable co-solvents are lower alkyl alcohols and mixtures thereof. The co-solvent may constitute 5 to 40% w/w of the formulation, though preferably less than 20% w/w of the formulation. Antioxidant stabilisers may be incorporated in such solution-formulations to inhibit deterioration of the active ingredient and are conveniently alkali metal ascorbates or bisulphites. They are preferably present in an amount of up to 0.25% w/w of the formulation.
Such self-propelling formulations may be prepared by any method known in the art. For example, the active ingredient (either as particles as described hereinbefore in suspension in a suitable liquid or in up to 20% w/w solution in an acceptable co-solvent, as appropriate) is mixed with any other constituents of the pharmaceutically acceptable carrier. The resulting mixture is cooled, introduced into a suitable cooled container and propellant is added thereto in liquid form; and the container is sealed. Alternatively, such self-propelling formulations may be prepared by mixing the active ingredient either in particles as hereinbefore described or in 2 to 20% w/w alcohol or aqueous solution as appropriate, together with the remaining constituents of the pharmaceutically acceptable carrier other than the propellant; introducing the resulting mixture, optionally with some propellant, into a suitable container; and injecting the propellant, under pressure, into the container at ambient temperature through a valve which comprises a part of the container and is used to control release of the formulation from it. Desirably, the container is purged by removing air from it at a convenient stage in the preparation of the self-propelling formulation.
A suitable container for a self-propelling formulation is one provided with a manually operable valve and constructed of aluminium, stainless steel or reinforced glass. The valve should, of course, be one having the desired spray characteristics of particle that which delivers a fixed amount of the formulation on the occasion of each operation of the valve, for example, about 50 to 100 microliters of formulation in each delivery; metered-dose devices are well known to those skilled in the art.
Formulations of the present invention may also be in the form of an aqueous or dilute alcoholic solution, optionally a sterile solution, of the active ingredient for use in a nebuliser or atomiser, wherein an accelerated air stream is used to produce a fine mist consisting of small droplets of the solution. Such formulations usually contain a flavouring agent such as saccharin sodium and a volatile oil. A buffering agent such as sodium metabisulphite and a surface active agent may also be included in such a formulation which should also contain a preservative such as methylhydroxybenzoate.
Other formulations suitable for nasal administration include a powder, having a particle size of 20 to 500 microns, which is administered in the manner in which snuff is taken, ie by rapid inhalation through the nasal passage from a container of the powder held close up to the nose.
In addition to the aforementioned ingredients, the formulations of this invention may include one or more additional ingredients such as diluents, buffers, flavouring agents, binders, surface active agents, thickeners, lubricants, preservatives eg methylhydroxybenzoate (including anti-oxidants), emulsifying agents and the like. A particularly preferred carrier or diluent for use in the formulations of this invention is a lower alkyl ester of a C18 to C24 mono-unsaturated fatty acid, such as oleic acid, for example ethyl oleate. Other suitable carriers or diluents include capric or caprylic esters or triglycerides, or mixtures thereof, such as those caprylic/capric triglycerides sold under the trade name Miglyol, eg Miglyol 810.
Any other therapeutic ingredient may comprise one or more of the following: antibiotic, antifungal and antiviral agents.
According to the present invention there are therefore provided:
(a) a novel compound of formula (I), including the compounds of formula (IA) or a salt thereof and (IB);
(b) a method for preparing a compound of formula (I), such as by esterification of a compound (IA) to prepare a compound of formula (IB);
(c) a pharmaceutical formulation comprising a non-toxic, effective amount of a compound of formula (IB) and a pharmaceutically acceptable carrier therefor;
(d) a method for preparing such formulations;
(e) a method for the prophylaxis or treatment of inflammation in a mammal, including man, comprising the administration to said mammal of a non-toxic, effective anti-inflammatory amount of a compound of formula (IB);
(f) a method for the prophylaxis or treatment of immunoregulatory conditions in a mammal, including man, comprising the administration to said mammal of a non-toxic, effective immunomodulatory amount of a compound of formula (IB);
(g) a compound of formula (IB) for use in medicine, such as in the inhibition of inflammation and/or the modulation of the immunoregulatory system;
(h) the use of a compound of formula (IB) in the preparation of a medicament, such as for the treatment or prophylaxis of inflammation and/or conditions associated with hyper or hypostimulation of the immune system; and
(i) the use of a compound of formula (IA) in the preparation of a compound formula (IB).